Sodium Nitroprusside Enhances Contractions of the Guinea-pig Isolated Vas Deferens

The effects of sodium nitroprusside on the electrical and mechanical properties of the smooth muscle of the guinea-pig vas deferens, and its responses to transmitter substances, have been investigated by use of the sucrose-gap technique. Isolated longitudinal segments of guinea-pig vas deferens contracted in response to electrical field stimulation (100 V, 0.04–0.1 ms, 1–5 Hz, 10 s train every 60 s) and application of ATP (1 mM) or noradrenaline (10 μM). Sodium nitroprusside (0.1 mM) did not affect resting tension but did enhance contractions evoked by electric-field stimulation but not by ATP or noradrenaline. The sodium nitroprusside-induced enhancement was unaffected by the nitric oxide synthase inhibitor, Nω-nitro-L-arginine methyl ester (L-NAME) (0.1 mM). Conversely, electrically evoked contractions were unaffected by the nitric oxide precursor L-arginine (1 mM) or the nitric oxide donor S-nitroso-N-acetyl-DL-penicillamine (SNAP) (0.1 mM). The amplitudes of electrically evoked excitatory junction potentials (EJPs) were not affected by application of sodium nitroprusside, although it caused a small depolarization of 0.7 ± 0.3 mV. Similarly, the depolarization caused by exogenous application of ATP or noradrenaline was unaffected by the presence of sodium nitroprusside. L-NAME, L-arginine and SNAP did not affect EJP amplitude or baseline membrane potential. It is concluded that sodium nitroprusside enhances electrically evoked contractions of the guinea-pig vas deferens by reducing the threshold voltage for action potential firing in smooth-muscle cells.     

Iron Metabolism and Liver Disease. Proceedings of a Festschrift for Professor June Halliday (Part 2)

This companion article to 'Career Paths for Medical Research' (F. Gasmenterol. Hepatol. , issue 9) comprises the text of papers presented at the Symposium held as a Festschrift to celebrate the distinguished career and contributions of Professor June Halliday. The contributors include leading international, national and local experts in iron metabolism and their presentations are in the form of up-to-date reviews or, in some cases, original unpublished contributions to the field. As such, the proceedings represent a comprehensive 'mini-textbook' of recent advances in iron metabolism with particular reference to iron storage disease. The articles should, therefore, be of wide interest to readers of the journal.     

Costs of Magnetic Resonance Imaging Services in Public Hospitals

Audited cost data from two public hospital installations participating in a trial of the utilisation and efficacy of magnetic resonance imaging are presented. The data cover the period July 1987 to June 1988 when both installations had attained stable patterns of operation. One hospital operated a superconductive system and the other a resistive magnetic resonance imaging unit. Depreciation and salaries represented the major components of cost.     

Tumour suppressor genes and colorectal neoplasia

Two distinct gene classes have been implicated in colorectal carcinogenesis. Tumour promoter genes (oncogenes, dominant oncogenes) produce an excessive positive stimulus to cell proliferation. The ras family of oncogenes are an example. Acquired mutations of the c-k-ras gene are commonly found in colonic adenomas and carcinomas. Tumour suppressor genes (anti-oncogenes, recessive oncogenes) normally constrain or regulate cell proliferation. Loss of this function through gene deletion or mutation is oncogenic. Inherited tumour suppressor gene mutations have now been identified in several of the familial cancer syndromes. Acquired tumour suppressor gene mutations are found in both sporadic and hereditary cancers. Together with the tumour promoter genes they provide the genetic basis for the cellular changes occurring during carcinogenesis. The retinoblastoma gene was the first human tumour suppressor gene to be characterized and exemplifies the class. More recently, linkage studies in the hereditary cancer syndromes and the detection of specific deletions in sporadic tumours have helped to identify several new tumour suppressor genes. At least four of these (MCC, APC, p53 and DCC) apparently contribute to sporadic colorectal carcinogenesis. Germ line APC mutations produce the inherited colorectal cancer syndrome familial adenomatous polyposis (FAP). Detection of these mutations using linked markers has already found clinical application in the screening of families with this disease. In the future, genetic diagnosis of hereditary non-polyposis colorectal cancer (HNPCC) and the recognition of those genetically susceptible to sporadic colorectal cancer may become possible. At the same time, as our understanding of the genes involved improves, new avenues for treatment and prevention of colorectal cancer may emerge.     

Respiratory allergy and month of birth

A total of 476 patients with respiratory allergy were interviewed to establish whether the season of birth influenced the type of allergy experienced. Patients with perennial symptoms did not differ from the general population of the U.K. in the distribution of their months of birth. Patients with summer seasonal symptoms attributable to grass pollen sensitivity were more likely to have been born in December to February than in August to November. This trend was most significant in female patients who did not have associated perennial symptoms and who developed symptoms early in life. Other significant differences were also noted between groups of patients complaining of the same symptoms. More males than females had summer seasonal symptoms whereas more females than males had perennial symptoms. Patients who had both perennial symptoms and summer seasonal exacerbations had a higher incidence of a positive family history of atopy and developed symptoms earlier in life than those patients who had summer seasonal or perennial symptoms only.     

A yaws campaign in Sierra Leone

An account is given of the methods employed and the results obtained in a campaign against yaws in an area of Sierra Leone containing about 276,000 people.